Vibration isolation systems are employed in a wide variety of applications to minimize the transmission of disturbances forces between two bodies or structures. For example, satellite are often equipped with vibration isolation systems to minimize the transmission of vibratory forces emitted from attitude adjustment devices (e.g., control moment gyroscopes or reaction wheel arrays) to other vibration-sensitive components (e.g., optical payloads) carried by the satellite. The performance of a vibration isolation system is largely determined by the number of isolators included within the system, the manner in which the isolators are arranged, and the vibration attenuation characteristics of each individual isolator. Vibration isolation systems employing three parameter isolators, which behave mechanically as a primary spring in parallel with a series-coupled secondary spring and damper, provide superior attenuation of high frequency vibratory forces as compared to vibration isolation systems employing other types of passive isolators, such as viscoelastic isolators. An example of a three parameter isolator is the D-STRUT® isolator developed and commercially marketed by Honeywell, Inc., currently headquartered in Morristown, N.J. Such isolators are often passive, single Degree of Freedom (DOF), axially-damping devices well-suited for usage within multi-point mounting arrangements.
While providing the above-noted advantages, passive three parameter isolators remain limited in certain respects. When tuned to provide optimal damping at a frequency corresponding to a targeted critical mode, the three parameter isolator will provide less-than-optimal damping at other operational frequencies and critical modes. This can be disadvantageous in that multiple critical modes can exist over a broad frequency range, the precise frequencies of the critical modes may not be known until after isolator deployment (e.g., satellite launch), and the frequencies at which the critical modes occur can vary over time with changing loads, imbalances, bearing imperfections, and the like. As another limitation, the dynamic stiffness of a conventional three parameter isolator is typically fixed by isolator design and by the viscosity of the selected damping fluid. Thus, a conventional three parameter isolator generally cannot provide both a relatively soft in-orbit stiffness (as is often desired to allow the attenuation of low amplitude vibrations), while also providing a relatively high on-launch stiffness (as may be desired to decrease the likelihood of fluid leakage when the isolator is subject to high impact loads during satellite launch).
It is thus desirable to provide embodiments of a three parameter isolator or isolator assembly that overcomes the limitations associated with conventional passive three parameter isolators of the type described above. In particular, it would be desirable to provide three parameter isolator assemblies that enable the damping and stiffness characteristics of the isolator assembly to be actively tuned during usage of the isolator assembly; e.g., by way of non-limiting example only, it may be desirable to provide an isolator assembly enabling adaptive tuning of damping/stiffness properties during on-launch and in-orbit operation of the isolator assembly when deployed onboard a spacecraft. It would also be desirable to provide embodiments of a vehicle isolation system employing one or more three parameter isolator assemblies providing such in-field tuning. Other desirable features and characteristics of embodiments of the present invention will become apparent from the subsequent Detailed Description and the appended Claims, taken in conjunction with the accompanying drawings and the foregoing Background.